The present invention relates generally to a valving device for fluid control applications and, more particularly, to such a valving device having a pressure balanced bellows or bellows assembly.
The use of a bellows assembly within a valve is known. In valving applications, high cycle life may be difficult to achieve when the valve is subjected to high end or cyclical operating pressures. Accordingly, the bellows is preferably designed to be thin and flexible. However, the bellows may also function as a fluid barrier, and thus, the wall of the bellows may be subjected to a pressure differential. In this regard, the wall of the bellows may be designed to be thicker and less flexible, thus decreasing cycle life. To overcome this problem, various approaches have been developed to balance the pressure acting on the walls of the bellows.
In an automobile exhaust gas cleaning system, an exhaust gas recirculation valve (EGR valve) is used. The function of the EGR valve is to recirculate a part of the exhaust gas from the exhaust system to the intake system in accordance with negative pressure in the carburetor. Conventional diaphragm balanced valves, of which many are known in the art, are popular choices for EGR valves. Bellows type valves have been used, but the extreme temperature environments and pressure fluctuations present in the exhaust gas environment typically limits the effectiveness of the conventional bellows type valves.